Area Forecast Discussion
Issued by NWS Riverton, WY
FXUS65 KRIW 261708 AAA
Area Forecast Discussion...Update
National Weather Service Riverton WY
1110 AM MDT FRI AUG 26 2016
.SHORT TERM...Today Through Sunday Night
A trough axis continues to move through the area this morning, with
some continued shower and thunderstorm activity anticipated across
the eastern half of the state. A drier west-northwest flow will
develop over the area late tonight to help taper off remaining
A shifting flow is then anticipated over the area through the
weekend as a ridge develops over the state. Widespread dry
conditions are anticipated across the state. Temperatures will be
able to warm under the current pattern. Periods of gusty wind may be
possible across southern and western Wyoming on Saturday afternoon.
The combination of dry conditions, warming temperatures, and gusty
wind may increase fire weather behavior for areas impacted with the
stronger wind. Stay tuned for updates regarding this potential
.LONG TERM...Monday Through Friday
Synopsis...Dry weather with above normal temperatures and generally
light wind are expected Monday and Tuesday. Southwest flow will
bring chances of showers and thunderstorms across the west and south
Wednesday through Friday. Southwest winds will increase Wednesday
through Friday bringing elevated fire weather conditions to portions
of south and central Wyoming. A cooling trend is expected toward
the end of the week.
Discussion...The synoptic pattern to start this period on Monday
features a ridge across the east central Pacific, upper trough off
the west coast, and broad ridge from the Rockies across the southern
and central U.S. Upper trough is expected dig along the west coast
through Thursday with upper ridge amplifying across the central U.S.
in response. Deterministic runs of the GFS and ECMWF continue to be
more progressive moving west coast trough inland than their ensemble
means, but have trended slower.
Backing flow is shown to draw up some sub-tropical moisture into
southern Wyoming by Wednesday, while SW flow ejects a series of
shortwaves NE across the Intermountain West into the northern
Rockies. Thus, low chances of showers and thunderstorms expand
across the south and west Wednesday through Friday while most of
central Wyoming is expected to be under the influence of drier SW
flow. Lee side trough will be a surface feature Wednesday through
Friday with breezy conditions expected across Sweetwater, SE Fremont
and Natrona counties along with elevated to possibly critical
fire weather conditions.
Isolated to locally scattered convection is expected this afternoon
across the entire area with the best shot for thunderstorms along and
east of the Divide. Winds will generally be light except for gusty
and erratic winds to 35KT associated with thunderstorms. Convection
is expected to dissipate by 06Z Saturday. VFR conditions are expected
except for brief MVFR/IFR conditions in fog or convection. Mountain tops
will occasionally be obscured. Mainly VFR conditions are expected during
the day Saturday.
Lingering showers and thunderstorms will be found today, as a wave
of low pressure works its way through the remainder of the state.
Gusty wind and small hail may be possible with any storm development
today. A drier flow is expected behind the exit of this
system...with dry and warming conditions generally anticipated this
weekend. The opportunity for some afternoon gusty wind will be found
across southern and western Wyoming Saturday afternoon. This may
increase fire behavior across portions of the state, though this
situation will continue to be monitored.